Military operations suspended for 72 hours, state media reports, in announcement coinciding with start of Eid al-Fitr.

The Syrian government has violated a three-day ceasefire with air strikes and shelling in the country's Aleppo province, according to the United Kingdom-based Syrian Observatory for Human Rights.

War planes dropped bombs on the northern Aleppo area on Wednesday, while government forces fired shells in the nearby town of Anadan.

At least two children were killed by rebel forces who shot shells into the town of al-Zahra, the Observatory said.

President Bashar al-Assad's government had earlier in the day unilaterally declared the three-day ceasefire, which is set to last until the end of Friday, according to the state-run news agency SANA.

The ceasefire coincides with the start of the Eid al-Fitr festival, marking the end of the Islamic holy month of Ramadan.

A 72-hour "regime of calm" will be applied across the country until midnight on July 8, the Syrian army said in a statement republished in local media.

In a statement posted online, the Free Syrian Army (FSA) rebel coalition said it agreed to the Eid holiday ceasefire.

"Until now, (the government) has not abided by what it has announced, in that it has launched a number of attacks in various areas today," the statement said.

The statement said the rebel alliance welcomed international efforts that had led to the announcement from the government of Syrian President Bashar al-Assad, but that attacks had not ceased as a result.

Jaish al Islam spokesman Islam Alloush said: "The regime has made this announcement purely to escape international pressure. On the ground, I don't think anything has changed."

Jaish al Islam said in a separate statement that, despite the announced truce, government and allied forces had attacked the town of Maydaa, in the Eastern Ghouta area east of Damascus. Maydaa has been held by Jaish al Islam.

A cessation of hostilities brokered by foreign powers in February to facilitate talks to end the five-year civil war has mostly unravelled in areas where it took effect in the west of the country.

That truce was agreed with many opposition militias, but did not include the al-Qaeda-affiliated al-Nusra Front or the Islamic State of Iraq and the Levant (ISIL, also known as ISIS).

Since then, the Syrian army and the Russian military, which supports Syrian President Bashar al-Assad, have announced a number of temporary local truces in areas of intense fighting.

But air strikes and fighting have often continued in spite of the declarations.

Syria's conflict started with largely unarmed protests in March 2011, but it quickly turned into a full-scale civil war. More than 270,000 people have been killed throughout the five-year period, according to the Syrian Observatory.